Mechanical Stretch Of Pulmonary Vein Induces Expression Of MMP-9 And TGF-β1 In Pulmonary Hypertension Due To Left Heart Disease In Rats

Background:The pathogenesis of pulmonary hypertension due to left heart disease(PH-LHD)is unclear.Transforming growth factor-β1(TGF-β1)and matrix metalloproteinase-9(MMP-9)both play an important part in pulmonary vascular remodeling,which is the pathological basis of PH-LHD.Pulmonary venous hypertension is the earliest pathophysiological change during the development of PH-LHD,and whether pulmonary venous hypertension in the early stage of the disease is involved in subsequent pulmonary artery remodeling has not been reported.Objectives:This study was aimed to evaluate the role of MMP-9 and TGF-β1 in mechanical stretching-induced remodeling of pulmonary veins in the early stage of PH-LHD.Method:Forty-eight male Sprague-Dawley rats were randomly divided into sham group(including S1,S2,n=6)and PH-LHD model group(including M1-M6,n=6).The sham group received sham surgery.The PH-LHD group received banding procedure.On day 25 pulmonary venous rings were prepared in both groups after Doppler echocardiography and hemodynamic examination.The S1 and M1 groups served as control and were given a mechanical strength of 0 g for 30 minutes.The S2 and M2 groups were given a mechanical strength of 0.5 g for 30 minutes.The M3-M6 groups were pretreated with MEK1 inhibitor,p38 MAPK inhibitor,JNK inhibitor and stretch-activated channel(SAC)inhibitor for 30 minutes respectively,followed by a mechanical tension of 0.5 g for 30 minutes.The expression levels of mmp-9 and TGF-β1 in serum or pulmonary venous smooth muscle were determined by ELISA,RT-q PCR and Western Blot.Result:1.PH-LHD rat model was established by Banding procedure.(1)Compared with sham group,PH-LHD model group showed significantly lower rate of weight growth and increased heart weight.(2)On day 25 doppler echocardiography showed that PH-LHD model group had left heart failure.(3)On day 25 the RVSP was significantly increased in PH-LHD model group by right heart catheterization.2.MMP-9 and TGF-β1 expression levels were increased in the early stages of PH-LHD.(1)On day 25 the results of ELISA showed that the serum levels of MMP-9 and TGF-β1 in PH-LHD group were significantly higher than those in sham group.(2)On day 25 the results of RT-q PCR showed that the levels of MMP-9 and TGF-β1 in the pulmonary vein tissue of PH-LHD model group were significantly higher than those in sham group.3.mechanical tension can induce the expression of MMP-9 and TGF-β1 in isolated pulmonary veins of PH-LHD rats.Western blot showed:(1)The expression levels of MMP-9 and TGF-β1 was similar between the S1(sham+ 0g)and the S2(sham+ 0.5g)groups(n=6,P>0.05).(2)The expression levels of MMP-9 and TGF-β1 in the M1(Banding+ 0g)group were higher than those in the S1(sham+ 0g)group(n=6,P<0.05).(3)The expression levels of MMP-9 and TGF-β1 in the M2(Banding+ 0.5g)were higher than those in the M1(Banding+ 0g)group(n=6,P<0.05).4.The increased expression of MMP-9 and TGF-β1 in isolated pulmonary veins of PH-LHD rats induced by mechanical stretchcan be antagonized by SAC/MAPKs signaling pathway inhibitors.Western blot showed:(1)The expression levels of MMP-9 in M4(Banding+ SB203580)and M6(Banding+ SP600125)were lower than M2(Banding+ 0.5g)(n=6,P<0.05 vs.M2);(2)The expression levels of TGF-β1 in M5(Banding+ streptomycin)and M6(Banding+ SP600125)were lower than M2(Banding+ 0.5g)(n=6,P<0.05 vs.M2).Conclusion:In the early stage of PH-LHD,the expression of MMP-9 and TGF-β1 were increased in pulmonary vein,which could be promoted by mechanical stretch.Pulmonary vein mediates the increased expression of MMP-9 and TGF-β1 through activation of SAC/MAPKs signaling pathway and participates in pulmonary vascular remodeling of PH-LHD.